This proposal describes a 5 year career development and research plan to train the Candidate as an independent epidemiologic researcher with a focus on HIV neuropathogenesis and neurocognitive outcomes in HIV-infected children. The Candidate will answer key questions addressing the benefit of antiretroviral therapy (ART) on preservation and salvage of neurocognitive development, and the role of systemic monocyte activation as a potential mechanism of HIV-induced neurocognitive impairment. The training plan builds on the Candidate's research expertise in HIV pathogenesis, pediatric HIV and epidemiology, and will improve her understanding of HIV neuropathogenesis and its relation to cognitive development in children. The proposal provides a foundation with which the Candidate will develop an independent research program in pediatric HIV, with an emphasis on neuropathogenesis and neuroepidemiology. The mentoring plan integrates a highly productive collaboration between pediatric HIV researchers from the Kenya Research Program with institutional excellence in neurology and neuropsychology at the University of Washington. Additional expertise in neurocognitive assessments in Africa from the University of Minnesota will complement this mentoring plan. Research Plan - HIV compromises neurocognitive development in children and some neurocognitive deficits may persist despite ART. In particular, sustained immune activation, in spite of successful virological and immune response to treatment, may limit the benefit of ART. We will utilize existing and novel pediatric HIV cohorts to undertake new neurocognitive studies. In Aim 1, we will determine the extent to which early ART started in infancy preserves long-term neurocognition and will identify prevalence, types and cofactors of neurocognitive deficits. In Aim 2, we will determine prevalence and correlates of neurocognitive deficits in children diagnosed later in childhood who initiate ART and are followed thereafter. In Aim 3, we will determine the relative influence of viral, immunologic and immune activation on neurocognitive outcomes in each group of HIV-infected and treated children. We hypothesize that early- and late-ART can salvage neurocognitive outcomes and that longer duration of systemic monocyte activation will correlate with severity of neurocognitive deficits. We anticipate that data from these studies will inform interventions to optimize neurocognitive outcomes in children with HIV. This training opportunity will result in the Candidate developing an independent translational research program focused on mechanisms and prevention of neurocognitive impairment in HIV-infected children.